Partially folded states of the cytolytic protein sticholysin II

• Published in: Biochimica et biophysica acta 2001-02, Vol.1545 (1-2), p.122-131
• Main Authors: Mancheño, J M, De Los Ríos, V, Martínez Del Pozo, A, Lanio, M E, Oñaderra, M, Gavilanes, J G
• Format: Article
• Language: English
• Subjects: Anilino Naphthalenesulfonates - metabolism; Circular Dichroism; Cnidarian Venoms - chemistry; Hemolysin Proteins - chemistry; Hydrogen-Ion Concentration; Osmolar Concentration; Protein Conformation; Protein Folding; Protein Structure, Secondary; Protein Structure, Tertiary; Sodium Chloride - pharmacology; Spectrometry, Fluorescence; Structure-Activity Relationship; Temperature
• ISSN: 0006-3002; 0167-4838
• DOI: 10.1016/S0167-4838(00)00269-7

Sticholysin II (Stn II) is a cytolytic protein produced by the sea anemone Stichodactyla helianthus, its effect being related to pore formation. The conformation of the protein and its temperature-induced transitions, in the 1.5-12.0 pH range and in the 0-0.5 M NaCl concentration interval, have been studied by circular dichroism and fluorescence spectroscopy. At temperature < 35 degrees C, the protein maintains the same, high beta-structure content, folded conformation in the 1.5-11.0 pH range and ionic strength up to 0.5 M. In the 1.5-3.5 pH range and ionic strength > or = 0.1 M, Stn II shows a thermal transition, resulting in a partially folded state characterized by: (i) a native-like content of regular secondary structure, as detected by far-UV CD; (ii) a largely disordered tertiary structure, as detected by near-UV CD, with partially exposed tryptophan residues according to their fluorescence emission; and (iii) ability to bind the hydrophobic probe 2-anilinonaphthalene-6-sulfonic acid. In the pH range 4.0-10.5, thermally-induced protein aggregation occurs. The obtained results demonstrate the existence of partially folded state of Stn II, which may contribute to the pore formation ability of this cytolysin.